Workpiece expansion compensator for resistance heating apparatus

ABSTRACT

An improvement which permits automatic compensation for longitudinal workpiece expansion in a resistance heating apparatus of the type wherein a workpiece is transversely gripped between two pairs of spaced apart resistance heating contacts during heating. The improvement comprises mounting one of the pairs of contacts in a manner to be transversely movable relative to the other pair of contacts in a direction generally axial to the workpiece as it expands longitudinally during heating. Force means are provided for the movable pair of contacts for selectively axially moving the contacts to the initial position following heating of a workpiece in preparation for heating another workpiece.

United States Patent Amosky et al.

[54] WORKPIECE ExPANsIoN COMPENSATOR FOR RESISTANCE HEATING APPARATUS [75] Inventors: Joseph E. Arnosky, Broadview Heights; Ronald A. Meermans,

Strongsville, both of Ohio [73] Assignee: Park-Ohio Industries, Inc., Cleveland, Ohio [22] Filed: Sept. 20, 1971 211 Appl. No.2 181,666

[52] U.S. Cl. ..2l9/156, 219/50, 219/161 [51] Int. Cl. ..C2ld 9/62 [58 Field of Search ..2l9/l56', 50, 56,

[56] ReIerenees Cited UNITED STATES PATENTS 1,679,730v 8/1928 MacDonald....'. ..219/156 3,418,447 12/1968 Rizzoloetal ..2l9/156 [in 3,737,619 [45] June5, 1973 4/1960 Stich etal ..2l9/l56 6/1920 MacDonald..... ..2l9/l56 Primary Examiner-J. V. Truhe Assistant ExaminerL. A. Schutzman Attorney-Meyer, Tilberry and Body [57] ABSTRACT An improvement which permits automatic compensat'ion for longitudinal workpiece expansion in a resistance heating apparatus of the type wherein a workpiece is transversely gripped between' two pairs of spaced apart resistance heating contacts during heating. The improvement comprises mounting one of the pairs of contacts in a manner to be transversely movable relative to the other pair of contacts in a direction generally axial to the'workpiece as it expands longitudinally during heating. Force means are provided for the movable pair of contacts for selectively axially moving the contacts to the initial position following heating of a workpiece in preparation for heating another workpiece.

6 Claims, 5 Drawing m...

YPATENIEUJ'JI 1w SHEEI 1 [IF 3 III II] A) [H1111 I I I INVENTOR.

JOSEPH E. ARNOSKY BY RONALD A. MEERMANS ATTORNEYS PATENIEUJ'JJ SUN-'1 3,737,619

SHEET 2 BF 3 FIG. 2

FIG. 4

I8 32 20 \EU 5% L E r INVENTOR.

JOSEPH E. ARNOSKY BY, RONALD A. MEERMANS Mew, 7M 8 Bad;

ATTORNEYS INVENTOR. I JOSEPH E. ARNOSKY BY RONALD A. MEERMANS 44 WM, 5: M,

ATTORNEYS WORKPIECE EXPANSION COMPENSATOR FOR RESISTANCE HEATING APPARATUS This application pertains to the art of resistance heating and more particularly to resistance heating appara- .;tus for elongated workpieces.

The inventionis particularly applicable for use as a workpiece expansion compensator in resistance heating apparatus used for heating elongated generally cylindricalworkpiecessuch as for example, steel shafts,

and will be described with particular reference thereto; however, it will be appreciatedthat the invention has broader applications and may be used in other instances where it is desired to employ resistance type heating to elongated workpieces having any cross sectional configuration.

Heretofore, resistance heating apparatus which have beenemployed for resistance heating elongated workpieces have been comprised of two spaced apart pairs of resistance heating contacts wherein at least one of the contacts in each pair was movable toward and away from its associated contact. In operation, a workpiece was first placed between the pairs of contacts in a desired spaced relationship therewith and the movable contacts directed toward their associated contacts so as to clamp the workpiece therebetween. A heating curtent was then applied to the workpiece through the heating contacts by means of an outside current supply source. Following heating, the movable contacts were retracted t;facilitate removal of the heated workpiece and insertion of a new unheated workpiece.

During heating, particularly-to the elevated temperatures often incurred during the heat treating of elongated steel shafts, an elongated workpiece experiences a certain amount of longitudinal expansion. It was therefore necessary, in order to prevent damage to the workpiece or to the heating apparatus, to provide means for compensating for this longitudinal expansion as it occurred. In the prior types of apparatus, this has been accomplished .by mounting the contact pairs so as --to permit slight transverse movement of each pair relative to the other. However, in using these means, the contact pairs were continuously biased toward each other and to a home positionby biasing means which oftentimes comprised spring members. Thus, as a workpiece was heated, the force exerted by the workpiece against the contact pairs during longitudinal expansion necessarily was required to overcome the force exerted in the opposite direction by the biasing'means.

This prior type of longitudinal expansion compensator had two principal drawbacks. First, it was necessary for *both contact pairs to move relative to each other such that any mechanical difficulty with one of the biasing means could affect the overall compensating ability of the .apparatus to the extent that the desired andlor necessary longitudinal expansion compensation could not be realized and the entire heating apparatus would be damaged. Second, and as these compensators continuously exerted a force against the contacts in a direction opposed to longitudinal expansion, the desireddegree of longitudinal expansion could not always having undesirable physical characteristics would often be generated.

The present invention contemplates an improvement to resistance type heating apparatus of the type hereinabove described which overcomes all of the above referred problems and others generally associated therewith and provides an improved longitudinal workpiece expansion compensating means which is readily adaptable to present resistance'heating apparatus, isadjustable to permit compensation for any length of expansion and provides means which do not interfere with the ordinary workpiece expansion during heating.

In accordance with the present invention, there is provided an improvement used in compensating for longitudinal expansion of an elongated workpiece during heating. The improvement is directed for use in resistance heating apparatus of the type utilizing first and second pairs of heating contacts spaced axially of the workpiece and where at least one contact of each pair of contacts is movable between a first open condition and a second workpiece clamping and heating condition with the workpiece extending therebetween. The compensating means permits one of the pairs of contacts to move unrestricted away from the other pairs of contacts from a first spaced normal position in a direction generally axial to the workpiece during heating thereof and includes separate means for selectively forcing the one pair of contacts axially back to the first position following heating and return of the one pair of contacts from the second to the first condition.

In accordance with another aspect of the present invention, there is provided a method of resistance heating an elongated workpiece having an axis which comprises ,the steps of: clamping the workpiece between first and second pairs of electrical contacts at first and second positions respectively; passing electrical current through the contacts; allowing the first pair of contacts to move axially with the workpiece to a third position as the workpiece expands when the current is passed; and, separately moving the first pair of contacts from the third to the first position following heating of the workpiece.

In accordance with another aspect of the invention, the method further includes the step of moving the first and second pairs of contacts from a first opened condition to a second heating and clamping condition at the first position and from the second heating and clamping condition to the first opened condition at the third position. The step of moving the first pair of contacts from the third to the first position occurs at least after the pairs of contacts are moved from the second to the first condition.

The principal object of the present invention is the provision of a workpiece expansion compensator for resistance heating apparatus. 7

Another object of the present invention is the provision of a workpiece expansion compensator for resistance heating apparatus which presents substantially no resistance to longitudinal expansion of a workpiece during heating.

Still another object of the present invention is the provision of a workpiece expansion compensator for resistance heating apparatus which is adjustable so as to permit use with workpieces of various lengths and experiencing various degrees of longitudinal expansion.

Yet another object of the present invention is the provision of a workpiece expansion compensator for resistance heating apparatus which is readily adaptable to any resistance heating apparatus utilizing spaced contacts to grip a workpiece therebetween during heatmg.

The invention may take physical form in certain parts and arrangements of parts, a preferred embodiment of which will be described in detail in this specification and illustrated in the accompanying drawings which form a part hereof and wherein:

FIG. 1 is a side view of a resistance heating apparatus which includes the subject invention;

FIG. 2 is a plan view of the apparatus shown in FIG.

FIG. 3 is a cross sectional view taken along lines 33 in FIG. 2;

FIG. 4 is a cross sectional view taken along lines 4-4 in FIG. 1; and,

FIG. 5 is an enlarged plan view of the contact arm assemblies in order to show the subject invention in more detail.

Referring now to the drawings wherein the showings are for the purposes of illustrating the preferred embodiment of the invention only and not for purposes of limiting same, the FIGURES show an apparatus having a resistance heating portion A, workpiece supply area B, workpiece feeder system C, workpiece removal system D, electrical supply area E and apparatus framework F.

Specifically, and with particular reference to FIGS. 1, 2 and 5 and resistance heating portion A, it will be seen that it includes a pair of spaced apart contact arm assemblies 10,12 received on an elongated mounting T shaft 14 supported by apparatus framework F in any convenient manner. It is to be appreciated that assemblies 10,12 are identical to and oppositely disposed from each other so that description will hereinafter only be made with reference to assembly 10, it being I understood that assembly 12 is identical thereto unless otherwise specifically noted. Assembly includes a contact arm assembly hub 16 which comprises that portion of the assembly which is received over mounting shaft 14. The hub is received thereon in a sliding relationship so that assembly 10 may be easily moved longitudinally along the shaft in either direction. Pivotally mounted to the hub by convenient means are contact arms 18,20 which form a scissors-like assembly. A fluid cylinder 22 is operatively disposed between the contact arms at one end thereof to drive the other ends of the arms between an open and closed relationship relative to each other. It will be appreciated that fluid cylinder 22 may be comprised of any type of fluid cylinder, however, in the preferred embodiment, a pneumatic cylinder is employed and standard clevis type mountings are used to affix the cylinder relative to the contact arms. Disposed immediately adjacent contact arms 18,20 on hub 16 are a pair of spur gears 24,26 which intermesh with each other in order to assure unity of movement between arms 18,20 respectively (FIG. 3). Use of these gears is known for providing such unity of movement.

With particular reference to FIGS. 1 and 4, it will be seen that disposed on the opposite ends of contact arms 18,20 from fluid cylinder 22 are contact assemblies 28,30 respectively. This type of contact assembly is known and comprises insulators 32,34 spaced between the contact arms and copper contact blocks 36,38. The contact blocks include V-shaped workpiece receiving grooves 40,42 therein as is also known. Contact assemblies 28,30 may be made self-aligning by pivotally mounting them to arms 16,18 so they will at least pivot through a plane transverse to the plane of the associated contact arm assembly. The self-aligning feature permits compensation for workpiece run-out to assure the desired workpiece contact is obtained during heatmg.

To maintain contact arm assemblies 10,12 in the desired spaced apart positions along mounting shaft 14, split-block retainers 50 are used on eachside of hubs 16 as is best shown in FIG. 5. Each split block retainer is comprised of block halves 52,54 whichare closely received over shaft 14 and tightly drawn thereagainst by means of bolts 56 passing through halves 52 into halves 54. It should be noted that the retainers used with assembly 10 may be permanently affixed to the hub 16 associated therewith and that the retainers employed with assembly 12 are independent of the hub 16 associated therewith. It should further be noted that the retainer 50 associated with the outside end of contact arm assembly 12 includes an elongated block half or compensator base 58 in place of a block half 54. The

use of the elongated block half 58 will hereinafter be more fully described.

With particular reference to FIGS. 2, 3 and 5, it will be seen that disposed adjacent hub 16 of contact arm assembly 12 is a longitudinal expansion compensator generally designated 60. More specifically, compensator 60 includes a fluid cylinder 62 conveniently mounted to an end plate 64 of the hub. Cylinder rod 66 of the fluid cylinder has disposed adjacent the end thereof a generally circular pressure plate 68. A fluid passage 70 is employed when it is desired to expand the fluid cylinder in a known manner. The controls necessary to effect selective expansion and retraction of cylinder 62 are also known and therefore not shown. The use of expansion compensator 60 will be hereinafter more fully described relative to operation of the apparatus.

Workpiece supply area B (FIG. 1) is comprised of a workpiece magazine of any convenient type known for handling elongated steel shafts and which, in the preferred embodiment, comprises a gravity'feed magazine. As shown, the magazine includes a loading end 82 and a feeding end 84 disposed therebelow. As seen in FIGS. 1 and 2, a plurality of cylindrical steel shafts S are placed in the magazine in a side-by-side relationship. It should be noted that in this embodiment of the invention, all the workpieces are of the same length and of substantially the same diameter. Spaced immediately adjacent feeding end 84 is a shaft receiving head 86 which includes a generally U-shaped channel 88 therein adapted to receiving a single elongated shaft S. A fluid cylinder 90 is disposed therebelow and includes a cylinder rod 92 connected with the head so that in the retracted position of the cylinder", the head is immediately adjacent feeding end 84 to receive a workpiece S and in the extended position, the head is disposed adjacent resistance heating portion A. A head extension 94 is provided to extend between head 86 and cylinder 90 and acts to prevent other workpieces S from leaving the magazine when the head is moved to the extended position.

Workpiece removal system C (FIG. 1) comprises a roller conveyor generally designated 100. Conveyor includes elongated L-shaped channel members 102,104 having a plurality of roller elements 106 extending transversely therebetween. These rollers could be of several types, however, in the preferred embodiment, they comprise steel rollers which include a generally U-shaped necked portion 108 to accommodate and maintain workpieces S in the desired position as Electrical supply area D isconventional and therefore not shown in detail. It supplies 60 cycle electrical current through the necessary electrical cables to the contact assemblies. At the same time, and also as is conventional, coolant fluid is supplied through coolant supply lines (not shown) to maintain the contact assemblies below their melting temperatures.

Apparatus framework E includes a plurality of tubularvertical frame members, tubular horizontal frame members and tubular angle frame members. It is to be understood that the frame is designed so as to mount the individual component assemblies as hereinabove previously described in the required relative positions.

:Ei rther, it is possible to include a sheet metal cover around this framework so as to protect the components from destructive elements oftentimes found in industrial environments, to protect workmen coming into contact-with the apparatus and to present a single unit package. As the framework itself does not form a part of the present invention, it is not more fully described.

In describing the operation of the subject invention, reference will be made to one workpiece S and to FIGS. 1 2 and 5 It is first necessary to set contact arm assemblies 10,12 in the desired position axially ia long mopntingjshaft 14. Depending upon the length of workp eces S; to. be heated, the contact arm assemblies are positioned so that contact assemblies 28,30 will be "spaced immediately adjacent the end points of a workpiece placed in a heating relationship therewith. Once assembly 10,. is so positioned, bolts 56 are tightened so 'as' to bring block halves 52,54 of the two split-block retainers 50 into close clamping engagement with the mounting shaft in order to assure retention of the contact armasfsembly that position. The split-block retainer 50- associated with the inside of contact arm assembly 12 is, then similarly. placed in a clamping relationship with the shaft as hereinabove described. It should be noted: again that retainers 50 associated with assembly 10 are affixed to the-hub l6 and that retainers 50 associated with assembly 12 may be spaced along shaft 14 independent of the associated assembly. Retainer5 0. associated with the outside of hub 16 for assembly 12 is moved to a spaced apart position from the assembly a distance slightly greater than expected axial movement ofthe hub due to the force created by expansion of a workpiece S during heating. This distance isfeasily ascertainable from engineering tables or from the resultsof previously conducted test heatings. With contact arm. assembly. 10 permanently located and with cQI l CE arm assembly 12 disposedagainst its inner retainer. 50, the, apparatus is, in readiness for heating a workp e In. order to feed a workpiece into a heating position, cylinders 22 are moved to the retracted position in order that contact assemblies 28,30 are, movedto. a first or opened condition. In this condition, fluidcylinder 90 is energized so that one workpiece Swill be carried in U-shaped channel 88 into proximity with resistance heating portion A. Head extension94 retains there mainder of the workpieces in the magazine during ,this extension. When the workpiece is in proximity with the contact assemblies, fluid cylinders 22 are energised to the extended position in order that contact assemblies 28,30 are moved to a second or closed condition with workpiece S clamped therebetween in V-shaped grooves 40,42 respectively. Fluid cylinder 20, may then be retracted in order that another workpiece. S will be received in U-shaped channel 88 in readiness for another cycle. With workpiece S clamped between the contact assemb liesof contact arm assemblies 10,12 electrical energy may be supplied thereto in a known manner to effect resistance heating of the workpiece.

During this heating, and as hereinabove stated, workpiece S will experience a certain amount of longitudinal expansion. In using the subject invention, and with reference to FIG. 5, it will be seen that contact arm assembly 12 is free to move longitudinally away from contact arm assembly 10 along shaft 14. The motive force for this movement is provided by the workpiece S itself as it expands. As shown in FIG. 5, this expansion carries the entire contact arm assembly a distance a asshown therein. Once heating is complete, the electrical energy supply may be de-energized, cylinders 22 retracted to move the contact assemblies to the first or opened con- "the extended position so that pressure plate 6 8 er gages the inner surface of block half or comperrsatorbase 58.] In the preferred embodiment, base 5 8,l ineludes a hole 120 therethrough to receive the end of cylinder ro'df66 in order that pressure plate 68 may be receivedf flush against the inside edge of the base. The force exerted by expanding cylinder 62 with pressure plat @8 li g against base 58 is sufficient to move assembly 1'2"0nj its slidable mounting with the associated hub16 tothe initial position with the hub engaging the associated inner retainer 50. At this point, assemblies 10,12 are again spaced apart from each other the desired..initial 'dis tance so that another workpiece S maybe fed from; supply area B into proximity with resistanceheatingportion A as hereinabove previously described. I :1

During at least the feeding. period, it is advantageous to maintain cylinder 6 2 in the expanded position in order that contact arm assembly 12 will, be positively retained in its home position against the inner; retairier. Once cylinders 22 havebeen energized; to move the contact assemblies to the second. or closed; condi tion, cylinder 62 may be moved to the retracted position in order that contact arm assembly 12 will befree to move away from contact arm assembly 10: during heating as hereinabove previously described, [t a n.

be noted that there is a small space between pressure plate 68 and base 58 when cylinder 62 is in the retracted position and after assembly 12 has been forced away from assembly during heating. This space assures that the longitudinal expansion compensator 60 will not interfere with the heating process should there be, for some reason, additional expansion realized in a particular workpiece.

The invention has been described with reference to the preferred embodiment. Obviously, modifications and alterations will occur to others upon the reading and understanding of this specification. It is my intention to include all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.

Having thus described my invention, I now claim:

1. In a resistance heating apparatus for heating an elongated workpiece having an axis wherein said apparatus includes first and second pairs of heating contacts spaced axially of said workpiece and at least one contact of each pair of contacts being movable between a first opened condition and a second workpiece clamping and heating condition with said workpiece extending therebetween and means for supplying electrical energy to said pairs of contacts for heating said workpiece when said pairs of contacts are in said second condition, the improvement comprising:

compensating means for allowing said first pair of solely caused by longitudinal expansion of said workpiece during said heating and separate means for forcing said first pair of contacts axially back to said first position following heating of said workpiece and return of at least said first pair of contacts from said second condition to said first condition, said force means being selectively energizable between non forcing and forcing conditions.

2. The improvement as defined in claim 1 wherein each contact of said first and second pairs of contacts is received on a mounting shaft, said compensating means including means for allowing said unrestricted movement of each contact of said one pair of contacts longitudinally along their mounting shaft and means for fixedly securing each contact of said second pair of contacts in a direction longitudinally along their mounting shaft.

' 3. The improvement as defined in claim 2 wherein said forcing means comprises a fluid cylinder disposed in an operative relationship with said first pair of contacts.

4. The improvement as defined in claim 3 wherein said first and second pairs of contacts are disposed on a common mounting shaft, said forcingmeans further including an adjustable stop received on said shaft adjacent said first pair of contacts for cooperation with said fluid cylinder.

5. The improvement as defined in claim 4 wherein said first pair of contacts are mounted to said mounting shaft by a single contact mounting unit, said fluid cylinder being disposed in said unit and including means for controlling said cylinder for retaining said cylinder in a retracted condition when said unit is moved axially away from said first normal spaced position during heating and for expanding said fluid cylinder to engage said stop in order to force said unit back to said first position when said first and second pair of contacts have been moved to said first condition from said second condition following heating.

6. A method of resistance heating an elongated workpiece having an axis, said method comprising the steps of:

clamping said workpiece between first and second pairs of electrical contacts at first and second posi-' tions respectively;

passing electrical current through said contacts;

allowing said first pair of contacts to move axially unrestricted with said workpiece to a third position as said workpiece longitudinally expands during said step of passing, said expansion providing the only force for moving said first pair'of contacts to said third position;

unclamping said workpiece from between said first and second pairs of electrical contacts at said third and second positions respectively; and, separately moving said first pair of contacts from said third to said first position following said step of unclamping.

7. The method as defined in claim 6 wherein said step of clamping comprises moving said first and second pairs of contacts from a first opened-condition to a second heating and clamping condition at said first and second positions and said step of unclamping comprises moving said first and second pairs of contacts from said second heating and clamping condition to said first opened condition at said third andsecond positions, said step of moving said first pair of contacts from said third to said first positions occurring at least after said pairs of contacts are moved from said second to said first conditions. 4

8. The method as defined inclaim 7 further including repeating said steps for each workpiece to be heated. 

1. In a resistance heating apparatus for heating an elongated workpiece having an axis wherein said apparatus includes first and second pairs of heating contacts spaced axially of said workpiece and at least one contact of each pair of contacts being movable between a first opened condition and a second workpiece clamping and heating condition with said workpiece extending therebetween and means for supplying electrical energy to said pairs of contacts for heating said workpiece when said pairs of contacts are in said second condition, the improvement comprising: compensating means for allowing said first pair of contacts to move unrestricted away from said second pair of contacts from a first spaced normal position in a direction generally axial to said workpiece during heating thereof, said movement being solely caused by longitudinal expansion of said workpiece during said heating and separate means for forcing said first pair of contacts axially back to said first position following heating of said workpiece and return of at least said first pair of contacts from said second condition to said first condition, said force means being selectively energizable between non forcing and forcing conditions.
 2. The improvement as defined in claim 1 wherein each contact of said first and second pairs of contacts is received on a mounting shaft, said compensating means including means for allowing said unrestricted movement of each contact of said one pair of contacts longitudinally along their mounting shaft and means for fixedly securing each contact of said second pair of contacts in a direction longitudinally along their mounting shaft.
 3. The improvement as defined in claim 2 wherein said forcing means comprises a fluid cylinder disposed in an operative relationship with said first pair of contacts.
 4. The improvement as defined in claim 3 wherein said first and second pairs of contacts are disposed on a common mounting shaft, said forcing means further including an adjustable stop received on said shaft adjacent said first pair of contacts for cooperation with said fluid cylinder.
 5. The improvement as defined in claim 4 wherein said first pair of contacts are mounted to said mounting shaft by a single contact mounting unit, said fluid cylinder being disposed in said unit and including means for controlling said cylinder for retaining said cylinder in a retracted condition when said unit is moved axially away from said first normal spaced position during heating and for expanding said fluid cylinder to engage said stop in order to force said unit back to said first position when said first and second pair of contacts have been moved to said first condition from said second condition following heating.
 6. A method of resistance heating an elongated workpiece having an axis, said method comprising the steps of: clamping said workpiece between first and second pairs of electrical contacts at first and second positions respectively; passing electrical current through said contacts; allowing said first pair of contacts to move axially unrestricted with said workpiece to a third position as said workpiece longitudinally expands during said step of passing, said expansion providing the only force for moving said first pair of contacts to said third position; unclamping said workpiece from between said first and second pairs of electrical contacts at said third and second positions respectively; and, separately moving said first pair of contacts from said third to said first position following said step of unclamping.
 7. The method as defined in claim 6 wherein said step of clamping comprises moving said first and second pairs of contacts from a first opened condition to a second heating and clamping condition at said first and second positions and said step of unclamping comprises moving said first and second pairs of contacts from said second heating and clamping condition to said first opened condition at said third and second positions, said step of moving said first pair of contacts from said third to said first positions occurring at least after said pairs of contacts are moved from said second to said first conditions.
 8. The method as defined in claim 7 further including repeating said steps for each workpiece to be heated. 